Hypertension is one of the major causes of end-stage renal disease (ESRD) in the general population, and the number one cause in Blacks. These two diseases are the major cause of morbidity and mortality in the United States, especially among African Americans. There is some preliminary evidence suggesting that some antihypertensive drugs may retard the progression of hypertensive renal disease, but no clinical trial has been conducted to test this hypothesis in African Americans, who are disproportionately affected by this ailment. This multicenter project (active enrollment phase completed) will compare the effects of two levels of blood pressure (BP) control and three different antihypertensive drug regimens on the rate of decline in glomerular filtration rate (GFR) in hypertensive African Americans 18-70 years of age, with clinically diagnosed hypertensive renal disease (GFR 25-70ml/min/1.73msq.) to try to find answers to: 1)Is the pathological lesion in hypertensive renal disease purely a result of persistent hypertension?; 2) Is one antihypertensive drug better than another in terms of preservation of renal function?, and 3) Is there a level of BP more suitable for the survival of the kidney as opposed to the generally recommended level of 140/90mmHg? Those who qualified, based on BP levels and GFR results, were randomized in a 3x2 factorial design to initial treatment with either an angiotensin converting enzyme inhibitor (enalapril), a calcium channel blocker (amlodipine), or a -blocker (atenolol) and to a mean arterial BP (Goal MAP) of either < 92mmHg or 102-107mmHg. Furosemide, doxazosin, clonidine, hydralazine, and minoxidil are sequentially added until the goal MAP is achieved. THE AASK ANCILLARY STUDY is a multicenter, ancillary study of the AASK Full-Scale Trial population. A subset of the patients from the main study (300 total patients or 100 patients/treatment arm) are studied in order to examine the effects of the three classes of antihypertensive medications used in the main AASK Study, on heart rate variability (HRV) in this patient population. It is hypothesized that long-term (1 year) -blocker treatment will lead to greater parasympathetic tone, compared to calcium channel blocker treatment, as reflected by a difference in HRV (by Holter monitor and EKG) in hypertensive African Americans with renal disease. found, it could translate into decreased morbidity in this patient population. The primary outcome measure will be HRV as measured by spectral analysis of the beat-to-beat variability of the RR interval, looking at the high frequency component in normalized form after one year. Statistical analyses, interpretation and data entry of all Holter monitor data will be performed at the Holter Core Laboratory, and then supplied to the Central Data Processing Center for the main study.